Bridged [18]annulenes. A study of the synthesis and properties of 12c,12d,12e,12f-tetrahydrobenzo[g,h,i]perylene and its analogs

ThDione: A Powerful Electron-Withdrawing Moiety for Push-Pull Molecules

A series of new push-pull chromophores based on a combined cyclopenta[c]thiophene-4,6-dione (ThDione) acceptor, N,N-dimethylaniline, N-piperidinylthiophene or ferrocene donors, and ethylene or buta-1,3-dienylene π-linkers has been designed and synthesized. Utilizing one or two ThDione acceptors afforded linear or branched push-pull molecules. Experimental and theoretical study of their fundamental properties revealed thermal robustness up to 260 °C, a electrochemical/optical HOMO-LUMO gap that is tunable within the range of 1.47-2.19/1.99-2.39 eV, and thorough elucidation of structure-property relationships. Compared to currently available portfolio of heterocyclic electron-withdrawing units, ThDione proved to be a powerful and versatile acceptor unit. It imparts significant intramolecular charge transfer and polarizes the π-system, which results in enhanced (non)linear optical response.

Heterocyclic Nanographenes and Other Polycyclic Heteroaromatic Compounds: Synthetic Routes, Properties, and Applications

Two-dimensionally extended, polycyclic heteroaromatic molecules (heterocyclic nanographenes) are a highly versatile class of organic materials, applicable as functional chromophores and organic semiconductors. In this Review, we discuss the rich chemistry of large heteroaromatics, focusing on their synthesis, electronic properties, and applications in materials science. This Review summarizes the historical development and current state of the art in this rapidly expanding field of research, which has become one of the key exploration areas of modern heterocyclic chemistry.

Strongly emitting fluorophores based on 1-azaperylene scaffold

A novel blue-emitting polycyclic aromatic system was synthesized via anion-radical coupling. Its efficient direct hydroxylation led to a phenol possessing an intramolecular hydrogen-bond system. Since the energy gap difference between the enol and keto forms of this molecule is very small, characteristic of ESIPT chromophores, bathochromically shifted fluorescence was not observed.

Synthesis and anti-Pneumocystis carinii pneumonia activity of novel dicationic dibenzothiophenes and orally active prodrugs

Dicationic carbazoles have been found to be highly active against a rat model of Pneumocystis carinii pneumonia (PCP). Unfortunately, amidoxime derivatives, designed as prodrugs, were inactive against PCP even though the corresponding amidines were highly active. In the present work, a series of 2,8- and 3,7-bis cationic dibenzothiophenes was synthesized and assayed for anti-PCP activity. Three of the compounds proved to be more potent and less toxic than a standard anti-PCP drug (pentamidine) when given intravenously. Unlike the carbazoles, a dibenzothiophene amidoxime prodrug given orally reduced the parasite load by more than 99%. While no quantitative correlation was seen between anti-PCP activity and DNA binding, a strong level of DNA binding was found to be necessary for antimicrobial activity.

Novel Self-Assembly of m-Xylylene Type Dithioureas by Head-to-Tail Hydrogen Bonding

Dithiourea 1a self-assembles to form an orthogonal dimer structure both in solution and in the solid state, wherein the four thiourea groups establish a closed network of hydrogen bonds through a head-to-tail binding mode. This novel dimer structure was elucidated on the basis of (1)H NMR spectra, vapor pressure osmometry, and X-ray crystal structure analysis. Furthermore, a series of m-xylylene type dithioureas were synthesized and their dimerization constants (K(a)) in CDCl(3) were determined by dilution experiments using (1)H NMR spectroscopy. The magnitude of the K(a) values are dependent on the steric bulk of the side chains, the acidity of the thiourea groups, and the weak intermolecular interaction between the benzene rings of the side chains and the m-xylylene spacer.

Synthesis, molecular modeling, and K+ channel-blocking activity of dequalinium analogues having semirigid linkers

Dequalinium [1,1'-(decane-1, 10-diyl)bis(2-methyl-4-aminoquinolinium)] is an effective blocker of the small conductance Ca2(+)-activated K+ channel. It has been shown that the number of methylene groups in the alkyl chain linking the two quinolinium rings of this type of molecule is not critical for activity. To further investigate the role of the linker, analogues of dequalinium have been synthesized, in which the alkyl chain has been replaced by CH2XCH2 where X is a rigid or semirigid group containing aromatic rings. The compounds have been tested for blockade of the slow after-hyperpolarization on rat sympathetic neurons. The most potent compounds have X = phenanthryl, fluorenyl, cis-stilbene, and C6H4(CH2)nC6H4, where n = 0-4. The conformational preferences of the compounds were investigated using the XED/COSMIC molecular modeling system. Although there is some dependence of the potency of the analogue on the conformational properties of the linker (X), overall, X groups having substantial structural differences are tolerated. It seems that X provides a support for the two quinolinium groups and does not interact with the channel directly. The intramolecular separation between the quinolinium rings, which is provided by rigid groups X, is not critical for activity; this may be attributed to the residual conformational mobility of the heterocycles and to the extensive delocalization of the positive charge. These two factors may permit favorable contacts between the quinolinium groups and the channel over a range of intramolecular separations.